The proposed project seeks to identify and to explain the features of glaucoma's optic nerve damage in experimental primate and human glaucoma. Its features will attempt to specify the types of retinal ganglion cells most likely to suffer damage early and late in the process. This aim will direct the search for better early phychophysical testing in human glaucoma. The study of chronic glaucoma damage histologically is correlated with the clinical appearance of the damage to improve clinical appreciation of glaucoma injury. The study will improve knowledge of the pathogenetic process by which elevated intraocular pressure causes the death of retinal ganglion cells. This information is both directly and indirectly vital to appropriate therapy of glaucoma. The study will examine in detail for the first time potential causes for the increased susceptibility to glaucoma damage found in aged, myopic, and Black persons. A method will be developed further by which the absolute size of objects in the fundus of the eye can be measured objectively. This will greatly improve the estimates of glaucoma damage in clinical practice, and can in addition be of benefit in other ophthalmic conditions, particularly in the follow-up of possible malignant melanoma.